US1878112A - Method of coating substances - Google Patents

Description

*nuenis. ooornn ANDMENAHEMMERLUB-SOBEL; or; CLEVELAND, OHIO, .nssrenons,

Nb arming;

Patented Sept. 26, 1932 FF'ETF S- 1 TO K-EMET- LABORATORIES, INC.,. A CQRPQR A'IION"OF;'NEW YORK METHOD or coA'rINe suBsrAnoEs i l -Tl1is invention relates to a method of coat ing substances With metal or metals of the alkali or alkaline-earth groupsyand With the oxids of such'me'tals.

to a method of making such elements, it Will hereafter be described in that connection, by Way ot suitable example.

Gathodesotthedull-emitter or Wehnelt typeerdi-n arily consist of a platinum or other metallic core, -usually in the formof a W1-I6'1 or ribbon, which has been coated with oxid of: some metal or metals, such as'fbar um, strontium, or the hlze. Several methodslha've "f heretoforebeen employed in the production ofisuch cathodes. One of the older processes is todip' the-Wire to be coated into a solution ot the nitrate of the-desired metal ormetals,

andthenfl decompose the nitrate by heating =in inert atmosphere inorderto' obtain the ox id. Ibis-ordinarily necessary to apply a considerable number of successive coats of oxid; in this .manner if a uniform 1 electron emission is :to be obtained frcm the finished "element-1n another method of producing an oxid coating the-heated Wire is brought into contact With solid p'arafiine in which is suspended aco'nsiderable amount of'barimn onstrontium carbonate, orithe like. The car- -bonates being decomposed, an 'ox1d1coat1ng remains. In thls case, also, a large number of successive coatings arerequired; Still a third method is to paint or coat the Wire With a solution of bariumaZide,.-and then apply heat in order'ito. decompose thecompoundto metallic barium, Which readily oxidizes.

Each of these methods is open to a number of objectives, and presents certain definite disadvantages. In the first two methods there F-is not only the already mentioned necessity for applying a large number of successive coatings of oxid if a stable or uniform electron emission is desired, Which is troublesome and expensive in itself, but there is the fur- 'ther difliculty that considerable quantities of Application fi led September 20,1327. Serial at. 220,532.

gas are apt -to-be occludedduring the'c'oating process. It is extremely difiicult', or impos;

PATENT one f sible, completely to remove this occluded gas C during the subsequent evacuationof the-tube,

and this may account, to-some extent, for-thefrequente'rra'tic behavior of cathodes made in this Way. Moreover, it is diflicult to make the coatings of uniform thickness ,and hot: spots and consequent burning out of the filament frequently occur. -With' regard to the third process, barium az ideis a highly explosive; compound; its preparation is con I respondingly 'diilicult, and" the process is so dangerous as to be highly unsatisfactory.

Our invention provides a means for applying metallic'oroxid coatings-to substances I ofany desired character." The methodis substantially free from the foregoing difii culties and objections; and results in-aimore uniform and adherent coating than has been (so far as We areraware) hitherto obtainable.

According to our invention We dissolve an alkali or alkaline-earth metal,'or a salt or oxid off'such ametal, in anorganici'solvent, either 'by direct solution in the caseof a metal compound; or by converting the metal to anorganic compound by' means of the solvent,

and solution'of the resulting compound, inthe caseiot a metal. Wethen apply the resulting solution to'the substance, :for example a cathode elementior filament-,which isto be coated. The solvent isflthen evaporated, by-

exposure to the air or otherwise, when a uniform v and adherent 1 coating of the dissolved: compound remains- In the event that a metal, or a. saltrnot'an oxid, Was employed,

the coatin'gmay be readily converted to oxid by. furtherv exposure to the air, or by heating in airor other oxidizing atmosphere it necessaryyu I Particular examples of methods of"carry-- ing-out ourinvention are as follows l i c 1. Barium iodide is'dissolved in ethyl alcoholto form asaturatedsolution? This solution isi'applied to; afil'ament element b'y dip ping, brushing, l-or oth'erWise.'.- The "element is then exposed-"to the air until the alcohol evaporates; The "element isithen heated, preferably by means of 1ts own 'resistance'to' an I electric current, 111 a'an oxldizmg atmos-fl phere in order to convert the barium iodide into emissive barium oxid. The resulting coating is firm, uniform, and adherent.

2. Barium oxid is dissolved. in ethyl alcohol and applied toa filament element in the same manner. Heating in an oxidizing atmosphere is generally unnecessary in this case.

3. Barium metal is treated with an excess ofethyl alcohol to form barium ethylate, which is dissolved in the excess alcohol to form a solution of bariumethylate; This solution is applied as before, andthe coating of barium ethylate which remains afterevaporation of the solvent is decomposed by heating to form the desired oxid coating,

.4; Barium metal-is dissolved-in an excess of acetone toform a solution inacetone of barium enol-acetonate, which is employed as -inExample 3 above.

It must be understood that the foregoing examples are merely illustrative of our in ventlon, which, is, of course, not limlted thereto.

Throughout the foregoing examples we have referred to the metal barium, or its salts or oxids,for the sake of uniformity. Calcium, strontium, or other metals of the alkaline-earth group, their salts or oxids, may replace, or be used in conjunction with, barium, or alternate coatingsofdifierent compositions, may be employed. The sameapplies, also, to alkali metals such as'sodium, potassium, etc., or their compounds. Vie

gfrequently employ solutions; containing-several of these metals, or apply alternate coat ings derived from different solutions.

According to our invention, also, when two or'moreseparate organic solvents are .miscible, we may employ a suitable mixture of solvent-sto replace a single one, and such a mixture is included by the term organic solvent? or the like as herein employed. j

With regard to the substance whichis to receive. a metallic or oxid coating, we may employ 'a'metal in the form of a wire, filament, ribbon, small tube or rod, plate,'orthe like. chromium alloys, are-good ,examplesof metals which'act satisfactorily inzreceiving and retaining the coating. Even more refractory metals, such as tungsten, molybdenum, tantalum, platinum, etc., are also suitable. Our invention, however is notc'onfinedto coating metallic substances. In some cases we wish.

to apply a metal or oxidcoating to a nonmetallic substance. such as porcelain, silica, and so forth; There are certain types of cathodes (used in the so-called heater tubes).

fin which the. emitting surface isnot identical with the heating element, but comprise a tube or. small cylinder, etc., which is heated by means of a separate filamentor heater arranged within it. Our invention is equally applicable to coating ,such emitting elements We have found that nickel, or nickel line-earth oxid material to form an electronemitting cathode element, which comprises treatingalkalineearth metal with an organic solvent to'form 'an'organic compound, dissolving said compound in excess ofsaid solvent," applying the resulting solution to the substance to be coated, and converting the resulting coating to oxid.

2. Process of coating a non-metallic'refractory element with. alkaline-earth oxid v material to form an electron-emitting cathode element, which comprises treating alka- 1 line-earth metal with an excess of organic solvent to form a solution, applying the solution to the non-metallic refractory element to be coated and converting the applied solution to anoxid coating. n

3. Process of coating a metallicelement with barium oxid material to form an electron-emitting cathode element, which comprises treating barium metal with an excess of ethyl alcohol to form a solution, applying :1

the solution to themetal to be'coated and converting the applied solution toian oxid coating; V V a 4:. Process of coating'a metallic element with barium oxidmaterial to form .an'electron-emitting cathode element, which com-- prises treating barium metalwith an excess. of acetone to form a solution, applying the solution to the metal to be coated and converting the applied solutionto an oxidcoat- ,5. Process ofcoating a metallic element.

with barium oxid material to form an elec-.-. tron-emitting cathode element, which comprises treating barium metal with an excess of a saturated aliphatic oxygen-containing organicsolventto' form asolution, apply-v 1 ing the solution to the metal to be coated and converting the applied solution to an :oxid coating.

In testlmony whereof, we aflix our signature. t

HUGH S. COOPER. MENAHEM MERLUB-SOBEL.